1. Technical Field
The present invention relates in general to reserving virtual connections having a designated Quality of Service (QoS) in an Internet Protocol (IP) network, and relates in particular to a system and method for reserving a QoS designated virtual connection in a network equipped with a reservation server.
2. Description of the Related Art
For a data transmission wherein a connection is first established before the transmission takes place, bandwidth is reserved along the connection path taking error checking into account. Protocols that employ such an approach use a call-connect packet to initiate a session and a connect-confirm response packet to complete the call sequence.
For connection-oriented systems, a virtual circuit (VC) between the two endpoints is allocated to determine a route at call set-up time. During call set-up all necessary resources on the virtual circuit are reserved and logical channels are allocated. Only when the connection is cleared are the reserved resources and logical channels are released.
For Asynchronous Transfer Mode (ATM) networks, a call set-up process is established using virtual paths/virtual circuits (VP/VC). All ATM communications are set up using a controlled method wherein user-specific subscriber options are identified and utilized in establishing each connection. Generally, connections are not established by end users but by network devices or nodes. It is becoming more common, however, to control packet-switched telecommunications directly at the IP network level, which allows end-users to directly establish connections.
A connectionless transmission that is used, for example, at the IP network level, is a form of packet-transmission that does not require communications between the end devices before the transmission of data. Such connectionless packet-transmission employs no virtual circuit and is well-adapted to transmit short messages composed of a limited number of packets. In simple bus or ring networks, there is no problem implementing connectionless systems because the path-choice is limited. In meshed and complex networks, however, the significant problems arise. First, each router must possess substantial processing intelligence for processing the packet header. In addition, the network requires an efficient mechanism to ensure that all routers or nodes have an up-to-date information relating to the overall topology.
The Resource Reservation Protocol (RSVP) is a network-control protocol that enables IP applications to obtain special Qualities of Service (QoS) for their data flows. RSVP produces connection-oriented like communications having an established QoS. RSVP is not however a routing protocol. Instead, it works in conjunction with routing protocols and installs the equivalent of dynamic access lists along the routes that routing protocols calculate. RSVP can be used by end-users to reserve bandwidth within all routers included on the path to the destination. The limitation of RSVP is that if the bandwidth is already used, there is no way to add more reserved communications. In addition, there is no end-user avenue for requesting additional bandwidth.
Another problem with conventional reservation protocols such as RSVP is that they do not provide sufficient scalability since each request is handled by each network device or node in the path used by the connection.